Compressor unloading means



Feb. 15, 194-9. w, GlBSON 2,462,039

COMPRESSOR UNLOADING MEANS Filed Aug. 2-2, 1946 4 Sheets- Sheet 1 I N VEN TOR.

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' COMPRESSOR UNLOADING MEANS Filed Aug-22, 1946 4 Sheets-Sheet 2 IN V EN TOR.

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Feb. 15, WM. w. F. GIBSON COMPRESSOR UNLOADING MEANS '4 Sheets-Sheet 3 Filed Aug. 22, 1946 INVENTOR.

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Feb. 15, 1949. w. F. GIBSON 2,462,039

COMPRESSOR UNLQADING MEANS 4 Sheets-Sheet 4 Filed Aug. 22. 1946 INVENTOR. WILLIAM. E GIBSON.

Patented Feb. 15, 1949 2,462,039 COMPRESSOR UNLOADING MEANS William F. Gibson,

Chrysler Corporation, corporation of Deiaware Dayton, Ohio, assignor to Highland Park, Mich, a

Application August 22, 1946, Serial No. 692,269

2 Claims.

My invention relates to the automatic control of the pumping capacity of small compressors such as used in refrigeration or air conditioning units of relatively small sizes. My invention is an improvement upon the invention disclosed and claimed in the patent to Neeson 2,185,473, dated January 2, 1940, and comprises means adapting the principles of the Neeson patent to unusually compact compressors. The invention of course may be used in larger sizes of compressors but its primary aim is to provide a smaller compressor with all of the advantages and functions which Neeson provided for larger sizes of compressors. Likewise it should be pointed out that the same physically dimensioned compressor having my invention may have a 1 H. P. motor at certain speeds such as 1,760 R. P. M. may have a 2 H. P. motor attached thereto which operates at 3,400 B. P. M. and so on so that in speaking of the various horsepowers mentioned above I do not intend to be limited thereto. Likewiseit is to be appreciated that the same compressor may be attached to an internal combustion engine capable of speeds such as 6,000 to 10,000 R. P. M. and the total horsepower required to drive the compressor would correspondingly increase. It should be appreciated that the term horsepower is used as a relative indication of the maximum tonnage of refrigeration since in general a 1 H. P. motor is required for a 1 ton refrigeration compressor and so on. The foregoing figures are meant to indicate the field of usefulness of my invention in compressors of small sizes with respect to the ordinary sizes of compressors for corresponding horsepower-tonnage ratios. Likewise it should be appreciated that while the primary field of usefulness of the invention is in the refrigeration and air conditioning arts, a compressor utilizing my invention may be found of value in any field where a gas must be compressed.

A principal purpose for which my invention has been developed is in the air conditioning of passenger automobiles or the refrigeration of small delivery trucks for perishab e commodities. One of the problems of such an application is to provide a compressor of sufficient capacity at idling or low traveling speeds of the internal 600 to 800 R. P. M. and is capable of far higher combustion engine driving the vehicle to provide the required amount of refrigeration, and which will be capable of maintaining a relatively constant compressing efiect throughout the higher ranges of speeds to a maximum speed of which the automotive engine is capable. An engine of this type idles at relatively slow speeds such as speeds such as 3,600 to 7,000 R. P. M. Thus if an ordinary compressor is applied to such a use it must be capable of producing the maximum desired refrigeration at idling speed, for example two tons of refrigeration at 800 R. P. M. Such an ordinary compressor would therefore produce approximately 10 tons of refrigeration at an engine speed of 4,000 B. P. M. when the vehicle is traveling at 50 miles per hour. The 10 tons is not only five times more refrigeration than desired so that the compressor would have to cycle on and offin short bursts of operation, but the engine would be subjected to terrific overloads at higher operating speeds. The sudden shocks of application of this overload would be extremely dangerous to both the engine and the compressor. Therefore the primary object of my invention is to provide a compressor which will maintain a constant output, i. e., will have a capacity of two tons at idling speeds and will maintain a capacity of two tons up to the highest operating speed of the vehicle.

An object of the present invention relating to the foregoing is the protection of the automotive engine against ordinary careless driving practices. that it should not be done, it is very common to observe a vehicle driver start his engine and press the accelerator to the floor board several times in rapid succession. If this were done with an. ordinary compressor attached to the engine severe damage might result since the engine would be expected not only to overcome its own sluggishness when cold but to operate the compressor against its maximum load. An object of my invention is to provide a compressor which will permit of a greater chance that no damage will be done under such careless handling.

A further object of my invention is to provide a compressor having automatic capacity reduc-- tion of such small size that it may fit between the engine block and ornamental grill of an ordinary automotive veh cle or in other cramped quarters. The compressor herein illustrated is a two-ton. compressor adapted to be driven by external means such as by an internal combustion engine. having 6 cylinders with automatic capacity reduction means applied to each cylinder. the overall dimensions of which are approximately 11 inches from end to end and 10 inches maximum diameter. While I have illustrated a six-cylinder compressor, it is to be appreciated that the invention may be applied to a compressor of fewer or more cylinders.

Although it is well known to most drivers The foregoing objects and advantages of my invention will be more readily understood by reference to the accompanying drawings wherein like numerals refer to like parts throughout. In the drawings, Fig. l discloses a preferred embodiment of my invention taken substantially along the longitudinal center line thereof in a plane determined substantially by the linel-ll of.Fig. 2. Fig.2'is an end view of the compressor-looking at the front cover thereof. Fig. 3 is the opposite end view. Fig. 4 is a partial cross-section taken substantially in the plane'sofsFig. ;1:and showing further details of an individual cylinder and unloading means. Fig. *5 is a view "taken. substantially along line 5 5 'cifFigq l.

The compressor comprises a main casting H to which is bolted a front'cover-zlliand' a rear cover l2. The main casting is provided with internally extending struts l3 supportinga journal M which holds spaced sleeve bearings I5 and I6 =adapted'to'support the greater portion of a crankshaft l'l having a reduced end l8 which extends outward through an opening in thecover l2. The'reduced-portion l8 extends through a "sealing device -29 such as disclosed in the patent to Christmanand'Mc'Cortney; N 0. 2,200,413, dated "May-14, '1940," so that the interior of the casing formed by the three separable castings may be sealed against the atmosphere. The reduced portionof the shaft lfl is adapted to be suitably";

drivenin any convenient 'manner, The crank shaft I! is provided witha'crank pin'25 surrounded by a sleevebearingi-B which supports theenlarged ends of the appropriatenumber of connecting 'rods' fl. Each connecting rod carries a "piston 28 which reciprocates within a cylinder =s1eeve'l28 which extendsthrough a suction annulus 30extendingcircumferentially around the interiorofthe casting'lfl. The outer end of the Lil Wentling application. 'The oil which is forced from the gear pump 48 passes through a discharge groove 60 which communicates with a passage 6! extending outward through the cover H to a radially extending passage 62 communicating with a longitudinal passage 63 which leads to the master valve of the unloader mechanism. The

dischargmgroovetfii! inthe pump cover also co i-- municates witha longitudinal passage 65 which leads to a vertically extending passage 66 having "one end terminating in a longitudinal bore 6? within :which-is mounted a ball thrust bearing for the pump assembly as more fully detailed in said Wentling application. The opposite arm of passage 66 leads to a longitudinally extending passagefili which carries the lubricant to the bearings 15,16 and 25 as more fully disclosed in therpatent to Neeson, No. 2,225,228, dated December 17, 1940. Oil which passes between the bearing surfaces returns to the sump portion 50 andis recirculated by the pump. While I have illustrated a pump of the type disclosed in the aforesaid Wentling-application it is to be appreciated that other types of unidirectional pumps may-be substituted therefor such as that disclosed in the patent to Neeson, No. 2,151, 282, dated 'March2l, 1939, so that regardless of the direcothers counter-clockwise revolution.

sleeveis associatedwith'a suction and discharge 'valveassemblyil mounted-within a cylindrical bore 32 extending radially inward through the casting ID. The valve assembly isretainedin 'po'sition by a safety Sp1ing 33WhiCh is held compressed -byabolt attached cylinder head34. De-

* tails of an appropriate '-valve-assemblynot herein "readilyapparent may be obtainedfrom the pat- :ent to"'NeesonJNo.i2,137;965, dated November 22, 1938, or the co-pen'ding application of Lickteig, :Serial'NoJ668,962,filed1May 10, 1946. 'The bore 32 is connectediby :aip'ipe' 36Lto the interior of a ring-shaped idischarge 531111111115 3'! which is i attached'toa suitable valve assembly 38 adapted to connect'the compressor'toa refrigeration system of any suitable compressor-condenser-expander type. Thegas-eompressed bythecompressor and utilized in the refrigeration system-returns to the compressor through" a .suction valve 39 which communicates 'with"the='interiorfof the suction annulus '3 0.

The crank pint 25 is provided with'a'pump'driving'pin which engages atcross bar lfi extending from a" stub shaftfli'l't'adapted to "drive-a gear i-pump dfi-having associate'dttherewith a reversing disk 49such asmore fullydisclosed-and claimed "in the 'co-pending:application of- Wentling, Serial "No."660,981, filedrA-pril 10,1946, Lubricating oil 'isvadapted to be'drawn from a sump space 50 --provided 'by the lewerm'ost portion of the rear cover IZthrOugh' a. passage "5! extending longitudinally'of the'wall ofthe casing I lland'leading to a passagefiz ext-ending vertically upward in the'front cover' II and-rcommunicatingwith a 7passages53:leading'to asuctionigroove' 54 inthe pump cover 55 as more"fully:discloseduin said" Asdisclosed in the patent to Neeson No, 2,185,-

473, dated January 2, 1940, the interior of the casing communicates with the suction annulus 3 througha suitable small opening or openings so that the interior of the end cover It is subjected to the same pressures as exist within the suction annulus. This pressure is a refl ction of the load upon the refrigerating system. At any given speed the pressure of the gas returning from the refrigerating system will be higher when there is a greater heat load upon the system than when there is a lesser heat load; therefore, the pressure within the end'cover I? will increase in proportion to the higher load. This pressure causes "a corresponding collapse of a flexible metallic bellows-Til extending outwardly through a boss H cast onto the cover l2. The inner surface of the inner end of the bellows "i0 is attached to a valve operating rod 12 and the outer surface of the inner end of the bellows 10 is attached to an adjusting rod 13 which extends beyond the compressor. The rod 13 extends through a threaded, longitudinally slotted member H which carries an .adjusting nut 15 .adapted to. operate against the wings of a washer T6 slidable longitudinally of the member 14 thereby to compress a spring 71 -which extends from the-member T6 to theinner end of the bellows "Hi. Longitudinal adjustment k of thenut 1'5 determines the degree of compres- '-si0n ofrthe spring 17 and hence the range of pres- =sures required tocollapse the bellows 16. As the bellows collapses "the rod 13 moves outward and aszit expands the rod moves inward. A guide nut 78 may be'adjustablypositioned on the end of rod 13 to guide it and to determine the amount to-which' the bellows 10 may expand inwardly. --Suitable adjustment 'of nut .lapsezthe bellows'lflifor a -a ently'appear.

1'8 may totally colpurposewhich will'presof a spring 95 which extends from a The inner end of operating rod 12 is pivotally attached to the short arm of a pair of cranks l which are pivoted at 2 to a fulcrum member 3 mounted upon the inner surface of the end cover 12. The long arms of the lever I are pin and slot connected to a longitudinally movable master valve 4 which extends through a longitudinal bore in the casing I into a longitudinal bore in a valve member 5 mounted in a cylindrical cavity 6 in the end of the casing III. The valve member 4 terminates in a pair of spaced lands l9 and 8B separated by a reduced portion 8i. The passage 63 previously described communicates with the annular space surrounding reduced portion BI by means of a slot 82 through the member 5. As the bellows Ill contracts and expands the crank I moves the valve member 4 in and out to variable extents but the pump 48 will always be in communication with the space surrounding portion 8|. As the land 88 moves longitudinally the space surrounding portion BI will communicate with a plurality of slots 90 in the member 5 each of-which communicates with one of a group of longitudinal passages 9i extendin through the member 5 into the end cover I l.

Each passage SI communicates with a passage 92 extending through the cover II to the outer end of a cylindrical cavity 93 adjacent each of the cylinders 29. The cavity 93 holds a piston 94 which is moved outwardly by the compression collar 96 on a longitudinally extending rod 91 to a portion of the wall of the annulus 30. If the particular groove 9!] is in communication with the space surrounding the reduced portion 8| pressure from the pump will be applied to the cylindrical space 93 to move the piston 94 and rod 91 inwardly. against the compression of spring 95. The rod Ell is pivotally connected at 98 to a yoke member 99, the arms of which extend to opposite sides of the cylinder 29. Referring more particularly to Figs. 4 and 5 it may be seen that each arm is bent downwardly at its end to provide an inclined portion I08 adapted to be moved radially outward as the arm moves outwardly when oil E pressure is relieved and the piston 9d permitted to move outwardly by the compression of spring 95, thus bringing the inclined portion it over an abutment lfll such as provided by the head of a rivet I02 extending through the wall of the annulus 30. Each portion Hill is provided with an upwardly extending lug I03 engaging the under surface of a ring IE4 surrounding the sleeve 29. The ring I04 is held against the lugs I93 by a spring IE5 compressed between the ring and a portion of the valve assembly. The ring IE4 is provided with a plurality of arms I06 which extend radially outward in close contact with the wall of the cylinder sleeve 29 in the space between the cylinder sleeve and the spring I115. The outer ends of the arms I06 extend through the slots in the valve assembly which provide the suction passages whereby gas may enter the interior of the cylinder sleeve 29 from the suction annulus 30. In the position illustrated in Fig. l the arms H36 are spaced from the inner surface of a suction ring valve IIlI which controls the passage of gas from the annulus to the cylinder. The piston 28 is shown at the bottom of its stroke which means that the suction valve I01 has been opened due to the greater pressure of the gas in the annulus 30 over the rarified gas caused by the expansion of the free space in the cylinder due to the retraction of the piston. As soon as the piston starts moving outward the pressure within the cylinder will become greater, thus closing the suction valve. As soon as pressure within the cylinder becomes great enough a discharge valve Hi8 will be lifted to permit the gas to be discharged to space 31! which communicates with the discharge pipe 36 and collector pipe 3?. When the piston commences to retract the greater pressure in space 3! will seat the discharge valve I08 and the cycle will be repeated. If however there is no oil pressure in the space 93 and the rod 91 will move outward thus causing the lugs I03 to raise the arms m6 whereby to hold the suction valve I91 permanently from its valve seats, thus causing permanent communication between the suction annulus 3E! and the interior of the cylinder sleeve 28. As long as this condition exists gas will enter the cylinder on the inward movement of the piston but will be forced back from the cylinder to the suction annulus on the outward stroke of the piston, thus nullifying the working efiect of the piston.

In the operation of the device the amount of work required of the compressor will determine the pressure of the gas within the interior of the casing, which determines the extent to which bellows ll] will be collapsed or expanded. The degree of collapse of the bellows I6 determines the position of the valve land MI. The land may be in such position as to uncover one or more of the slots 96 (there being six such slots for a six-cylinder'compressor, only one of which is herein illustrated for clarity). Each slot so uncovered permits the application of oil pressure to its associated piston fi l thus moving the inclined portion Itil to the left in Fig. 4 and permitting the spring Hi5 to move the arms iilt from engagement with the suction valve Ifi'l, thus causing the piston 28 to compress gas. It will be observed that the oil pressure exists only when the compressor crank shaft Ii is in operation, preferably the inherent characteristics of the construction being such that sufficient oil pressure to move the pistons 9 will not exist until a certain minimum speed of revolution has been achieved thereby causing the compressor parts to run freely under any load when the automotive engine is being cranked. As soon as the ignition is efiective and idling speed of the engine is achieved oil pressure will exist so that cylinders may be caused to operate against the compression load. At idling speed of the engine the entiresystem should be so designed that all of the pistons should operate to supply the maximum required refrigeration. Since the number of revolutions per minute is low the compressor will not displace a great volume of refrigerant gas and the load upon the refrigerating system will usually be greatest since a new supply of commodities may be placed in a refrigerator truck or the interior of an air conditioned tcnneau will be at its hottest point. Therefore, pressure of the gas in the suction annulus and the interior of cover I2 will be high and the bellows it will be collapsed to the greatest extent possible. This causes movement of valve rod i to the far right in Fig. l, uncovering all of the grooves and causing all of the pistons to compress refrigerant gas. As the speed of the engine increases or as the load on the refrigeration system drops at the same speed the pressure of the gas returned to' the compressor will be lessened, bellows ill will expand, land Bil will cut off one or more of the grooves 90 and one or more of the compression pistons will cease operating so as to maintain a substantially constant refrigeration output.

The positionaofinuta'limay be regulated so as to I determine the'degree of compression of Spring 11" thereby setting thepressures at which the valve willcause unloading-or loading of various cylinders against various types or capacities of refrigerating systems. Likewise the position of nut 18'may be so adjusted as to prevent the ct:- pansion of bellows it beyond a certain point, providing means whereby at least one or possibly several of the pistons will always operate. This latter feature may befound desirable in certain refrigeration applications.

Preferably I provide a, plurality of grooves H on a portion of the valve rod 4, which are adapted to :be engaged by a spring urged ball I l 6 retained inLa bore in the wall of casting It). This device provides means whereby the movement of the valve rod 4 occurs in definite steps. For example, it may require a change of two pounds per square inch in the suction pressure to cause movement of the valve rod to load or unload each cylinder, thereby preventing fluttering of the unloading mechanism.

It will be observed that I have provided a compressor comprising a, main casting supporting the 5 compressing mechanism consisting of a crank shaft andits journals and the piston, cylinder and valve assemblies, and the individual unloading mechanism associated with each compressing cylinder as well as the master valve mechanism for controlling the individual cylinder unloading mechanism. To this main assembly is attached one end cover having the oil carrying passages-and the oil pump. Assembly of the ill end-cover H to the casing completes the con- 1:".-

nections whereby oil pressure may be applied to the individual cylinder unloaders. The remainder of the mechanism may be assembled simply by inserting the valverod t into the longitudinal borein casing l0, and as" the end cover l2 carrying the pressure responsive bellows is brought into position slipping the slots of the crank i into position over the pins carried by the valve rod 4.

While I have illustrated and described herein a preferred embodiment which the invention may take it should be obvious to those skilled in the art that various modifications in arrangement and detail thereof may be accomplished. I claim as my invention all such modifications as come within the scope of the following claims.

I claim:

1. A compressor having a plurality of radially extending cylinders each of a plurality of which is adapted to be individually controlled to compress gas or to be unloaded, comprising a first assembly including a main casting, a crank shaft supported thereby, means forming a plurality of radially extending compression cylinders, compression pistons operatively connected to said crank shaft, suction valve and discharge valve assemblies carried by said main casting, a plurality of individual cylinder unloading means carried by said main casting, each comprising an unloader piston and means operated thereby to hold one of said suction valves open whereby to cause its associated compression piston to reciprocate idly, all of said unloader pistons extending toward driving connection'of said pump to said crank shaft when said castingand cover are'assembled,

means forming a plurality of unloader? cylinders' in saidcover, each'in-position' to receive one of.

said unloader pistons when'said casting andcover are assembled, said coverhaving a plurality of' passages therethrough whereby fluid pressurer created by said pump may betransmitted to said master valve and selectively therefrom-to said unloader cylinders; a second end coverfor-said main casting, asuction pressureresponsive device carried by said second cover and adapted to.

collapse or expand as thesuctionpressure of the compressor varies, and means operatively con-- necting said device to said master valve upon assembly of said second end cover to said main casting whereby to controlthe selecting-actionof said master valve.

2. A compressor having a plurality of radially extending cylinders-each of a plurality ofawhich. is

adapted to be individually controlled to compressgas or to be unloaded, comprising a. main casting, suction valves anddischarge valves carried by said casting, one of each of said valves being associated with each of said cylinders, a plurality of individual cylinder unloading means each operable to hold one of said suction valves open under predetermined compressor operating conditions and each including a piston, a master valve, a first end coverfor said main' casting, av lubricant pump carried by said end cover, said cover having a plurality of unloader cylinders therein adapted to receive said pistons when said casting and cover are assembled, said cover having a plurality of fluid flow connections associated with said pump, said master valve and said unloader cylinders so that fluid may be pumped to said master valve and from there toindividual unloader cylinders selected by said master valve,

a second cover adapted to be secured tosaid main casting on the end thereof opposite. said first cover, means responsive to compressor suction pressure carried by said second cover and means operatively connecting said last mentioned means to said master valve upon assembly of said second end cover to said main casting so that said last mentioned means is operable to control said master valve in response to compressor suction pressure.

WILLIAM F. GIBSON.

REFERENCES CITED The following references file of this patent:

UNITED STATES PATENTS are of record inithe. 

